The smallpox vaccine is viewed as the most successful vaccine in history.
Take a look at this quote from a Vox article today about Covid 19 vaccines:
"In thinking about how a Covid-19 vaccine would play out, it helps to look at lessons from other vaccines
The Covid-19 pandemic is unprecedented in many ways, so whatever scenario emerges will be unlike anything we’ve seen before. That said, there are some historical cases that can illustrate what could happen with a Covid-19 vaccine.
The most ideal outcome would be a vaccine akin to that for smallpox, rendering robust and near-lifelong immunity to the virus. With the smallpox vaccine, smallpox has become only one of two viruses to have been eradicated in the wild. “It’s obvious that we’re all aiming for a vaccine that is more like the smallpox vaccine,” Fitzpatrick said